Step 1: Cook the Noodles - Begin by bringing a large pot of water to a boil. Add the dangmyeon and cook according to the package instructions, usually about 6-7 minutes, until they are tender but still chewy. Once cooked, drain the noodles and rinse them under cold water to stop the cooking process. Set aside.
Step 2: Prepare the Sauce - In a small bowl, mix together the low-sodium soy sauce, gochujang, rice vinegar, and sugar. Stir until well combined and set aside.
Step 3: Sauté the Vegetables - In a large skillet or wok, heat the sesame oil over medium heat. Add the minced garlic and sauté for about 30 seconds until fragrant. Then, add the sliced onions, carrots, and bell peppers. Stir-fry for about 4-5 minutes until the vegetables are tender yet still crisp.
Step 4: Combine Noodles and Sauce - Add the cooked noodles to the skillet with the sautéed vegetables. Pour the prepared sauce over the mixture and toss everything together gently, ensuring the noodles and vegetables are evenly coated. Cook for another 2-3 minutes to heat everything through.
Step 5: Add Spinach and Serve - Finally, stir in the fresh spinach leaves and cook for an additional minute until the spinach is wilted. Remove from heat, and garnish with toasted sesame seeds before serving. Enjoy your delicious Korean noodles!